CHANGELOG.md

Change Log

Eclipse Paho MQTT C++ Library

All notable changes to this project will be documented in this file.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.

Version 1.5.0 - (2025-01-07)

• Code base updated to to C++17
  • Now a C++17 compiler is required to compile the library
• CMake minimum required version raised to v3.13
  • Need a fairly recent CMake for C++17 support (>= v3.12)
  • #504 CMake v3.13 allows INSTALL(TARGETS) to work outside the current directory.
• Clients always created for v5 persistence format, making it universal for any connection.
  • If the application specifies a version it is kept as a hint for default connections.
  • The version for the connection should be specified in the connect options.
• The create_options now have all the parameters to create a client.
  • Can specify Server URL, Client ID, and persistence in the create options.
  • New client constructor that takes just the options object
  • The client caches a const create_options struct with all the creation parameters
  • Client creation internally simplified without breaking the public API
• Expanded the message constmer to be a full client "event" consumer.
  • The events are for connected, connection_lost, disconnected, message arrived, and application shutdown.
  • The application can get client state change notifications without resorting to callbacks.
• There's a new persistence_type (std::variant) that can hold any of the persistence specifiers (none, file directory, or user interface).
• Most of the class static constants are now constexpr.
• Removed the fake ReasonCode::MQTTPP_V3_CODE. Now all reason codes in a v3 connection are SUCCESS.
• The mqtt::exception checks if the 'rc' return code actually contains a reason code error, amd if so, sets it as the reason code.
• property can now report the typeid of its contained value.
• The properties list implements a const iterator
• Added a to_string() and operator<<() for reason codes.
• thread_queue is now closable.
• Added documentation for UNIX domain sockets coming in with Paho C v1.3.14
• Removed the manual implementation of make_unique<>()
• Added create_options assignment operators.
• Fixed some corner cases for topic_filter::matches()
• Cleaned up and fixed a number of example apps.
  • Most apps now except a server URI from the command line
  • 'data_publish' example uses C++17 std::filesystem for creating a file-based encrypted persistence for messages.
• Updated local CI (buildtst.sh) for current compilers and unit tests.
• Reorganized the source repository
• Completely reformat the sources and added a .clang-format file (a project master and a slightly-different one for headers).
• Added GitHub CI Action, removing legacy Travis and Appveyor files
• #410 Added 'shutdown_event' to the event consumer and reworked consumer to prevent propagating exceptions on shutdown.
• #451 Added low keep alive to async_publish_time to test connected/connection_lost callbacks
• #503 Fixed issue that generated docs were empty.
• #518 Add function for checking async consumer event queue size
• #519 Fix potential deadlock in set_callback
• #524 Fixed copy and move operations for 'subscribe_options'. Added unit tests.

Version 1.4.1 - (2024-07-09)

• #458 Set 'disconnected' handler for the consumer queue.

Version 1.4.0 - (2024-06-16)

• Ability to build the Paho C library automatically (now working properly)

  • CMake 'PAHO_WITH_MQTT_C' option properly compiles the existing Paho C v1.3.13
  • Moved 'src/externals/' to top-level

• Reorganized the source tree:

  • Moved header files to top-level 'include/' directory.
  • Moved 'src/sampless/' to top-level and renamed 'examples/'

• Fixed and optimized 'topic_matcher' trie collection

• Added some missing Eclipse/Paho legal documents to the repo.

• Ran a spell-checker over the code and doc files.

• #498 Overloaded property constructor to also take a uint32_t

• #491 add topic_matcher.h to install

• #485 export dependencies

• #484 add token::get_message

• #480 Fixed Paho C version in 'install_paho_mqtt_c.sh' script.

• #473 Getter for the client's cached connect options.

• #466 Iterable string collection

• #416 Removed FindPahoMqttC.cmake. Using Paho C package directly.

Version 1.3.2 - (2023-12-05)

• #463 Fixed generator expression for older CMake
• #378 Bad LWT message in async_publish.cpp sample.

Version 1.3.1 - (2023-11-23)

• #462 Fix version string for version v1.3.x

Version 1.3.0 - (2023-11-22)

• Fixed building and using library as DLL on Windows with MSVC
• Updated License to Eclipse Public License v2.0
• Updated create and connect options to better deal with MQTT protocol version
• Defaulting connect version to v5 if specified in create options.
• Added a topic_filter class to match a single filter to specific topics.
• Added a topic_matcher class to create a collection of items in a trie structure that can contain items tied to topic filters. (Useful for queues or callbacks per-subscription topic).
• Minor tweaks to prepare for C++20
• Support for Catch2 v3.x for unit tests (v2.x also still supported).
• Changed the sample apps to use the newer "mqtt://" schemas.
• Connect option initializers for v5 and WebSockets.

Fixed Issues and Pull Requests:

• #343 async_client::try_consume_message_until taking single parameter fails to compile
• #445 Update properties when moving/copying connect options.
• #325 Cache connect options in client to keep memory valid for callbacks like SSL on_error()
• #361 Added missing LICENSE file to conform to GitHub conventions.
• #304 Missing create_options::DFLT_C_STRUCT symbol when linking with MSVC.
• #429 Remove declaration of connect_options::to_string() with missing implementation.
• #411 Missing virtual keyword for some client methods
• #444 Unit tests to check that connect options builder sets properties.
• #313 Get unit tests building on Windows. Needed to get rid of make_unique<> for Windows
• #397 Doc about clean session in connect_options.h is wrong
• #442 g++ complains with multiple definition of static constexpr for mixed C++11/17 builds
• #445Fix copy/move constructor for connect/disconnect opts with properties
• #425 Silence warning for unused variable rsp in class unsubscribe_response
• #440 Fix typos across the project
• #428 Fixed type in create_options.h
• #407 Fix nodiscard warnings in sync client
• #385 Thread queue deadlock with multiple consumers
• #374 Add Paho C as a submodeule
• #350 avoid adding Paho MQTT C library twice
• #253 implicit capture of 'this' via '[=]' is deprecated in C++20
• #337 copy/move of caPath_ in ssl_options
• #330 added /build/ folder to .gitignore
• #317 String constructor using just len instead of end iterator.
• #323 Added Session Expiry Interval to v5 chat sample to test.

Version 1.2.0 - (2020-12-27)

This release bring in some missing MQTT v5 features, brings in support for websocket headers and proxies, ALPN protocol lists, adds the builder pattern for options, and fixes a number of bugs in both the C++ library and the underlying C lib.

Requires Paho C v1.3.8

• Missing MQTT v5 features:
  • Ability to add properties to Subscribe and Unsubscribe packets (i.e. subscription identifiers)
  • "Disconnected" callback gives reason code and properties for server disconnect
• New create_options that can be used to construct a client with new features:
  • Send while disconnected before the 1st successful connection
  • Output buffer can delete oldest messages when full
  • Can choose to clear the persistence store on startup
  • Select whether to persist QoS 0 messages
• Started classes to create options using the Builder Pattern, with the create_options_builder, connect_options_builder, message_ptr_builder, etc.
• User-defined websocket HTTP headers.
• HTTP/S proxy support
• Added ALPN protocol support to SSL/TLS options
• SSL/TLS error and PSK callback support
• Update connection callback support (change credentials when using auto-reconnect)
• Updates to the sample apps:
  • Overall cleanup with better consistency
  • Example of using websockets and a proxy
  • User-based file persistence with simple encoding/encryption
  • Sharing a client between multiple threads
• Converted the unit tests to use Catch2
• All library exceptions are now properly derived from the mqtt::exception base class.
• [#231] Added on_disconnected callback to handle receipt of disconnect packet from server.
• [#211, #223, #235] Removed use of Log() function from the Paho C library.
• [#227] Fixed race condition in thread-safe queue
• [#224] & [#255] Subscribing to MQTT v3 broker with array of one topic causes segfault.
• [#282] Ability to build Debian/Ubuntu package
• [#300] Calling reconnect() was hanging forever, even when successful. In addition several of the synchronous client calls were hanging forever on failure. They now properly throw a timeout_error exception.
• Several memory issues and bug fixes from updated Paho C library support.

Version 1.1 (2019-10-12)

This release was primarily to add MQTT v5 support and server responses.

• MQTT v5 support:
  • Properties
    • New property class acts something like a std::variant to hold a property of any supported type.
    • New properties class is a collection type to hold all the properties for a single transmitted packet.
    • Properties can be added to outbound messages and obtained from received messages.
    • Properties can also be obtained from server responses to requests such as from a connect call. These are available in the token objects when they complete.
  • The client object tracks the desired MQTT version that the app requested and/or is currently connected at. Internally this is now required by the response_options the need to distinguish between pre-v5 and post-v5 callback functions.
  • MQTT v5 reason codes for requests are available via token objects when they complete. They are also available in exception objects that are thrown by tokens.
  • Support for subscribe options, like no local subscriptions, etc.
  • Sample applications were added showing how to do basic Remote Procedure Calls (RPC's) with MQTT v5 using the RESPONSE_TOPIC and CORRELATION_DATA properties. These are rpc_math_cli and rpc_math_srvr in the src/samples directory.
  • A sample "chat" application was added, showing how to use subscribe options, such as "no local".
• More descriptive error messages (PR #154), integrated into the mqtt::exception class. MQTT v5 reason codes are also included in the exceptions when an error occurs.
• Applications can (finally) get server responses from the various ACK packets. These are available through the tokens after they complete, as connect_response, subscribe_response, and unsubscribe_response.
• The topic objects can be used to subscribe.
• Applications can register individual callback functions instead of using a callback interface object. This allows easy use of lambda functions for callbacks.
• The connect options can take a LWT as a plain message, via connect_options::set_will_message()
• New unit tests have started using Catch2.
• Tested with Paho C v1.3.1

Version 1.0.1 (2018-12-12)

This is a bug-fix released aimed mainly at issues with the build system and working towards more "modern" usage of CMake. In addition:

• Support for Paho C v1.2.1
• Fixed a number of build issues, particularly on Windows
• Windows shared libraries (DLL's) now supported
• Several minor bug fixes

Version 1.0.0 (2017-07-23)

The initial Paho C++ Client library for memory-managed platforms (Linux, Windows, etc).

• Requires Paho C Client Library v1.2.
• MQTT 3.1 & 3.1.1
• SSL/TLS
• Asynchronous & Synchronous interfaces
• Persistence and off-line buffering
• Automatic reconnect
• High availability.